This invention relates to a sputtering apparatus and method, more particularly to a sputtering apparatus that deposits films by plasma-enhanced vapor-phase growth techniques, a sputtering method that uses the apparatus to deposit thin films such as insulating films (insulators) or dielectric films (dielectrics), insulating films or dielectric films such as piezoelectric films that are deposited by such sputtering apparatus and method, as well as piezoelectric devices that use the piezoelectric films, and an ink-jet apparatus that is equipped with the piezoelectric devices.
Conventionally, thin films such as piezoelectric films, insulating films and dielectric films are deposited by the sputtering method that deposits films by plasma-enhanced vapor-phase growth techniques or a sputtering apparatus that uses this method. In such sputtering method and apparatus, high-energy Ar ions or other plasma ions that are produced by plasma discharge in high vacuum are allowed to collide with a target, whereupon the constituent elements of the target are released and vapor-deposited on a surface of a substrate to form a thin film on it.
In the sputtering method and apparatus, in order to ensure the formation of thin films of good quality, sputtering is performed with a predetermined potential being applied to a surface of a substrate that is held on a substrate electrode positioned in a face-to-face relationship with a sputter electrode placed within a vacuum vessel (see, for example, JP 06-145972 A and JP 2002-129320 A).
The bias sputtering method and apparatus that are described in JP 06-145972 A are designed to form films of high quality by controlling the incident energy of positive ions that strike the substrate and in one example, the sputter electrode connected to a plasma generating RF power source is spaced from the substrate electrode connected to a DC power source or a RF power source for applying a positive bias, with a third electrode being inserted to surround the plasma discharge space between the sputter and substrate electrodes, and a target material is placed on a surface of the third electrode with a negative DC voltage being applied to the same.
In another example that is described in JP 06-145972 A, the substrate electrode is connected to a DC power source for applying a biasing DC voltage whereas the sputter electrode is connected to a RF power source and a DC power source, and a DC voltage smaller than a threshold for sputtering the target material and a DC voltage greater than that threshold are applied alternately by an alternately applying means and the circuit constant of a matching circuit (matching box) for the RF power source is varied in synchronism with a change in the DC voltage by a matching circuit control means.
In yet another example, the sputter electrode is connected to a REF power source whereas the substrate electrode is connected to a DC power source that applies a DC voltage and, in addition, the floating potential of the plasma discharge space is detected by a floating potential detection means or the value of an electric current flowing through the substrate is detected by a RF current detection means provided between the substrate electrode and the DC power source, with the DC voltage on the substrate electrode being controlled by a substrate potential control means on the basis of the detected floating potential or current value.
In the sputtering method and apparatus described in JP 2002-129320 A, a technique is proposed to prevent electrostatic breakdown of a thin film during sputtering; a target connected to a sputter power source for applying a plasma-generating negative voltage is spaced from a substrate on a wafer stage connected to a bias power source which is an AC power source for applying a biasing desired voltage, for example, a negative voltage or an AC voltage, and a control electrode is provided laterally with respect to the sputter space between the target and the substrate, which is then set at a floating potential and the control electrode is supplied with a control voltage that adjusts the potential of the substrate to approximately zero volts as sputtering is performed.